Method for casting a large lead anode plate

ABSTRACT

A method is provided for casting a large lead anode plate, which comprises controlling the pouring temperature most favorable to the pumping and pouring of the melt, pouring the melt through a pouring trough into a mold, and applying three stages of water cooling to the resulting casting.

United States Patent 11 1 1111 3,863,703

Nishimura a Feb. 4, 1975 [54] METHOD FOR CASTING A LARGE LEAD 2,070,8212/1937 Badger 164/135 X ANODE PLATE [75] Inventor: Yuki Nishimura,Takehara, Japan FOREIGN PATENTS OR APPLICATIONS 1,006,591 4/1957 Germany164/126 [73] Ass1gnee: Mrtsul Mll'llllg & Smeltmg (10., Ltd., 1,194,1036/1965 Germany 164/348 Tokyo, Japan Filed: 14, 1974 PrimaryExaminer-Robert D. Baldwin [21] Appl. No.: 442,575

52 U.S. c1 .Q 164/128, 164/130, 164/135, [57] ABSTRACT 164/348 [51 1111.c1 B22d 25/04, B22d 35/04 A methol pmv'dd for casmlg a large lea-dplate, Wl'llCh comprrses controlling the pourmg tern Field Of Searchperature most favorable to the p p g and p g 164/l35 322-326 348 of themelt, pouring the melt through a pouring trough into a mold, andapplying three stages of water cooling [56] References C'ted to theresulting casting.

UNITED STATES PATENTS 974,541 11/1910 Truswell 164/326 7 Claims, 5Drawing Figures BACKGROUND OF THE INVENTION Generally, lead anode platesare desirably flat, because the use of flexed lead anode plates inelectrolytic cells tends to cause short-circuits and channeling ofelectric current which decreases the electrolytic efficiency.Heretofore, anode'plates for use in lead electrolysis have been preparedby the steps of melting crude lead having a purity of 97.0 to 98.5percent, pouring the melt into a flat or vertical mold in a thickness ofabout 30mm, cooling the casting by water, and picking up the resultingcasting from the mold. In casting techniques of the prior art, however,the anode plates often have been picked up before they have beensufficiently cooled down. Because the cooling of the casting has notbeen adequate at the time and speed involved, a flexed anode plate isoften produced. The use of such anode plates causes a decrease inelectrolytic efficiency and thus it is necessaary to press the plateinto a flat form before installing the same in an electrolytic cell.

Further, when melted crude lead is pumped from a melting kettle to amold through a trough or a pipe, the discharge of a large amount ofmelted lead into a flat mold causes waving in the mold, resulting inroughness of the surface and/or overflow of the mold causing the castingto swell'over the edge of the mold, which phenomenon is referred to as apicture frame. On the other hand,when the melt is poured in a smallamount, there are disadvantages in that casting takes much time and thatthe melt tends to solidify during the pouring. Therefore, in the priorart the pouring trough was often provided with a screen so that the meltpassed a number of notches that were defined in the lower portion of thescreen to reduce the adverse effects described above, yet withoutsolving the problem.

Further, in coolinga cast anode plate, either using massive quantitiesof water or when partial cooling of only one side surface is employed,there is produced a substantial bending stress resulting in flexing ofthe anode plate, in accordance with cooling methods of the prior art.

BRIEF SUMMARY OF THE INVENTION The present invention relates to a methodfor casting large lead anode plates having a minimum degree of flectionin the resulting product.

More specifically, the method comprises controlling the temperature suchthat the lowest temperature employed is conducive to proper pumping andpouring of the melt, reducing the velocity of melt without decreasingthe volume of flow of melt when pouring melt into a mold, and thenapplying first and second stages of water cooling to a melt surfacefollowed by a third stage of water cooling to the mold back surface.

For these purposes the pouring temperature employed is within the rangeof about 340C to 350C, and the melt is preferably poured into a moldthrough a pouring trough provided with two screens, each having a numberof circular openings extending over the surface thereof.

The present invention further provides a casting method for producinglarge lead anode plates in dimensions of 1,150 X 1,000 X (25 39)m/m andin weight of 380-440kg during periods of about 12 to 14 seconds. Theplates so produced are particularly useful as components in electrolyticcells, such as batterys.

The invention will be more fully understood by reference to thefollowing more detailed description and drawings:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic drawingillustrating the pouring trough and the anode casting molds of theinvention;

FIG. 2 is a histogram illustrating the degree of flection of lead anodeplates of the invention (solid line) in comparison with that of theprior art (dotted line);

FIG. 3 is a schematic drawing illustrating a typical pouring trough ofthe prior art;

FIG. 4 is a plan view of screen 5 of FIG. 1, illustrating a preferredembodiment of the screen; and

FIG. 5 is an elevational view of a preferred embodiment of screen 3 ofFIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT In the production oflarge lead anode plates it has been the practice to pour melted crudelead into a suitable mold at a temperature of 365 to 375 C. In view ofthe fact that lower pouring temperatures are desirable for reducing thebending stress due to cooling and bearing in mind that the melt-ingpoint of pure lead is 327.3C, in accordance with the present inventionthe transportation and pouring of melted crude lead is held andcritically controlled within the range of 340 to 350C, which has beenfound to be the lowest temperature range at which no difficulty occursin the pumping and the pouring thereof. Moreover, the handling of themelt is facilitated by two screens in such form as shown in FIGS. 1,4and 5, the first positioned at about the midpoint of the trough and thesecond at about the discharge port of the pouring trough inorder toreduce the velocity of the melt without decreasing the volume of flowthereof.

Referring to FIGS. 1 and 5, melted lead flows in the direction of thearrow F in a pouring trough l which is provided with a screen 3, atsubstantially the midway position 2 so that it partially restricts theflow of melted lead, which nevertheless passes through a number ofcircular openings 3a defined in the screen 3. Trough I then changesdirection and diverts the flow of melt downwardly and to a dischargeport 4 of the pouring trough l, interrupted at this point by a screen 5(FIGS. 1 and 4) provided with a number of circular openings 5a definedin the screen 5 which is disposed at the discharge port 4 or at thevicinity thereof. Thereafter, the melted lead is poured into a mold atposition P Thus, it is possible to reduce the velocity of melted leadwithout decreasing thevolume of flow thereof.

In order to maintain the bending stress to the minimum, cooling iseffected separately through the melt surface and through the moldsurface, and the cooling through the melt surface is divided into firstand the second stages, wherein the amount of cooling water is carefullyadjusted. The cooling water is preferably at substantially normal roomtemperature, or below.

FIG. 1 shows a rotatable, cylindrical casting apparatus 6 whichcomprises 18 mold pieces at the positions P to P representing moldsegments which advance in the direction of the arrow R. When, forexample, mole P is filled from pouring trough l and then the mold isadvanced to the position P the first stage of cooling C is effected bypouring water onto the mold. When the mold advances to the position Pthe second cooling stage C is effected by pouring water onto the mold.While the mold advances from the position P to P the third stage ofwater cooling is effected by pouring water over the mold surface.Finally, the mold advances to the position P where the casting isremoved therefrom. The molds are not necessarily limited to 18 pieces,which are shown for illustrative purposes only, since molds havingdifferent numbers of pieces can be employed. Further, cooling positionsand the removal position of the casting are not limited to the positionsin FIG. 1, but may be selected appropriately in accordance with thisinvention.

The first stage of cooling is preferably conducted with water-in anamount of from about 1.0 to 1.5 liters per mold segment. It ispreferable that the first cooling be effected at as many points on thesurface of a particular mold segment as possible, and more than 10points are more preferably selected so that the cooling effect can beattained over all of the melt surface. Further, the first stage ofcooling is preferably conducted after the lapse of 2 or 3 minutes fromthe completion of the pouring of the melt.

The second stage of cooling is preferably conducted with water in anamount of 0.5 to 1.0 liter per mold segment and after the lapse of 30 to60 seconds from the completion of the first stage of cooling. The timeduration for application of the cooling water may be about 30 secondsboth in the first and second stages of cooling. The third stage ofcooling effected through the mold surface is preferably started afterthe lapse of 30 to 60 seconds from the completion of the second stage ofcooling and is conducted by applying water over all of the mold backsurface in an amount of 170 liters per minute.

A more specific embodiment of the present invention will be illustratedin comparison with a method according to the prior art. In this case, acasting apparatus having a capacity of producing a large anode plate of1,150 X 1,000 X (25-39)m/m and of 380-440 kg in from 12 to 14 seconds isemployed.

According to the present invention, a pouring trough l illustrated inFIG. 1 is employed, through which melted lead is poured into molds at apouring temperature of 340 to 350C, while water in an amount of 1.0 to1.5 liter/32 seconds is poured downwardly at 22 points of the meltsurface during the first stage of cooling; then water in an amount of0.5 to 1.0 liter/32 seconds is poured downwardly at 9 points of the meltsurface during the second stage of cooling; then water in an amount of340 liter/2 minutes is poured upwardly over all of the back surface ofthe mold during the third stage of cooling; and the casting finallyremoved.

According to a method of the prior art, the pouring trough 11illustrated in FIG. 3 is employed, through which melted lead is pouredinto molds at a pouring temperature of 365 to 375C, while initiallywater in an amount of 2.0 to 3.0 liters is poured downwardly at 22points of a melt surface and then water in an amount of 340 liters ispoured upwardly over all of the back surface to provide cooling, beforeremoving the casting.

The frequency distribution of the degree of flection of the anode platesobtained according to the present invention is'shown in FIG. 2, incomparison with that of the prior art. It is clear that the anode platesproduced according to the present invention are superior to those of theprior art. Particularly to be noted, the distribution of the preferredembodiment of the present invention (solid line) is clearly defined at alower flection degree than the distribution in the prior art (dottedline), and the average flection degree (about 2m/m) of the preferredembodiment of the present invention is one third smaller than that ofthe prior art (about 6m/m). The deviation in the flection degree of theembodiment of the present invention (about i lm/m) is one second smallerthan that of the prior art (about i 2m/m), and the maximum value offlection degree of the preferred embodiment of the present invention(3m/m) is much smaller than the minimum flection degree of the exampleof the prior art (Sm/m). Thus, the present invention provides animproved method for producing, with high reliability, an excellent largeanode plate having a small flection degree.

Resort may be had to such modifications and equivalents as fall withinthe spirit of the invention and the scope of the appended claims.

What we claim is:

1. A method for casting a large lead anode plate comprising:

providing at least one open topped anode plate mold;

providing a pouring trough opening into said mold;

transporting melted crude lead through said trough at a temperaturewithin the range of from about 340C to 350C;

reducing the velocity of the melt without decreasing the volume of flowof melt during pouring of the melt into said mold;

sequentially applying discrete first and second stages of water coolingto the melt surface and a third stage of water cooling to the backsurface of the mold; and

subsequently removing the cast plate from said mold.

2. A method according to claim 1, comprising pouring said melt into amold through a pouring trough provided with two screens, one at aboutthe mid position of the trough and the other at about the discharge portthereof.

3. A method according to claim 2 wherein said screens are provided witha number of circular openings extending substantially over the surfacethereof.

4. A method according to claim 1, wherein said melt is poured into amold through a pouring trough provided with two screens, each having anumber of circular openings extending substantially over the surfacethereof one at about the mid position of the trough and the other atabout the discharge port thereof; and cooling water is applied at therate of about L0 to 1.5 liters at more than 10 points on the meltsurface for about 30 seconds after the lapse of about 2 to 3 minutesfrom the completion of pouring of said melt, followed by a second stageof water cooling of the melt surface and a third stage of water coolingapplied to the back of the mold.

5. A method according to claim 4, comprising applying water at the rateof about 0.5 to 1.0 liter to a melt surface for about 30 seconds afterthe lapse of 30 to 60 seconds from the completion of the first stage ofwater cooling.

6. A method according to claim 4, comprising applying water at the rateof about I liters per minute over all of the mold back surface for 2minutes after completion of the second stage of water cooling.

3,863,703 6 7. A method according to claim 4, comprising applysecondstage of water cooling, and water at about 340 s Water at the rate ofabout to liters at 22 liters over all of the mold back surface for 2minutes in points on the melt surface for 32 seconds in the first stageof water cooling, water at about 0.5 to 1.0 liters the third Stage ofwater coolingat 9 points on the melt surface for 32 seconds in the 5

1. A method for casting a large lead anode plate comprising: providingat least one open topped anode plate mold; providing a pouring troughopening into said mold; transporting melted crude lead through saidtrough at a temperature within the range of from about 340*C to 350*C;reducing the velocity of the melt without decreasing the volume of flowof melt during pouring of the melt into said mold; sequentially applyingdiscrete first and second stages of water cooling to the melt surfaceand a third stage of water cooling to the back surface of the mold; andsubsequently removing the cast plate from said mold.
 2. A methodaccording to claim 1, comprising pouring said melt into a mold through apouring trough provided with two screens, one at about the mid positionof the trough and the other at about the discharge port thereof.
 3. Amethod according to claim 2 wherein said screens are provided with anumber of circular openings extending substantially over the surfacethereof.
 4. A method according to claim 1, wherein said melt is pouredinto a mold through a pouring trough provided with two screens, eachhaving a number of circular openings extending substantially over thesurface thereof one at about the mid position of the trough and theother at about the discharge port thereof; and cooling water is appliedat the rate of about 1.0 to 1.5 liters at more than 10 points on themelt surface for about 30 seconds after the lapse of about 2 to 3minutes from the completion of pouring of said melt, followed by asecond stage of water cooling of the melt surface and a third stage ofwater cooling applied to the back of the mold.
 5. A method according toclaim 4, comprising applying water at the rate of about 0.5 to 1.0 literto a melt surface for about 30 seconds after the lapse of 30 to 60seconds from the completion of the first stage of water cooling.
 6. Amethod according to claim 4, comprising applying water at the rate ofabout 170 liters per minute over all of the mold back surface for 2minutes after completion of the second stage of water cooling.
 7. Amethod according to claim 4, comprising applying water at the rate ofabout 1.0 to 1.5 liters at 22 points on the melt surface for 32 secondsin the first stage of water cooling, water at about 0.5 to 1.0 liters at9 points on the melt surface for 32 seconds in the second stage of watercooling, and water at about 340 liters over all of the mold back surfacefor 2 minutes in the third stage of water cooling.